1. Fields of the Invention
This invention relates to an agent for preventing plant virus diseases. Particularly, this invention relates to an agent for preventing plant virus diseases characterized in that the agent contains polylysine as an active compound.
2. Related Art Statement
Once a plant is usually infected with a plant virus disease, the whole plant is infected and easily dead. The plant communicates the disease to other healthy plants one after the other by contact or entomophilous contagion, as the result, a great deal of damage is done to the plants before the plants are croped or removed. As the viruses of these plant pathogens, tobacco mosaic viruses (abbreviated as TMV) which infect eggplant family plants, potato viruses (abbreviated as PVX), cucumber mosaic viruses (abbreviated as CMV) which infect eggplant, cucumber or rape family plants can be exemplified.
As preventing ways of these virus diseases, for example, for entomophilous infection such as the cucumber mosaic diseases caused by CMV, extermination of intermediate insects, change of seeding time to avoid the insect generating time, cultivation of bred plants and so on have been tried. However, these methods are insufficient to obtain good control effect. For preventing the spread of virus diseases, infected plants have been pulled out. However, it is difficult to prevent the flying of poisonous insects from other fields, so that the prevention is not effective for such a trouble.
On the other hand, TMV diseases which do not infect by entomophily but by contact contagion infect crops at work by contacting the viruses with agricultural machines or by mixing the viruses into soil. For preventing the diseases, the agricultural machines, the soil, working clothes, fingers, etc. are subjected to disinfection at a great cost and expensive labor. However, such methods are insufficient to prevent the virus diseases.
Furthermore, TMV having weakened poison has been lately tried to use for preventing TMV-tomato. However, there is no guaranty that the TMV having weakened poison effectively acts on another kinds of crops. On the contrary, there is the possibility that a tomato which has contacted with the virus makes a contagion source and that viruses having strengthened poison are mixed into the viruses having weakened poison when many tomato seedlings are inoculated with the latter virus. For these reasons, no viruses having weakened poison have come into wide use.
As described above, physical elimination or agronomic control are only considered as a counterplan for preventing the plant virus diseases under existing circumstances. However, the control effect is little, and extensive damage caused by the plant virus diseases is done to crops. Accordingly, the prevention of the plant virus diseases is an important subject for agriculture.
For the purpose of inventing the prevention agent for plant virus diseases, many antiviral activates prepared from many natural products or synthetic compounds have been investigated. As the result, some materials having the antiviral activity have been found. Firstly, as a so-called multiplication control agent which controls virus multiplication in plant bodies, materials similar to nucleic acids such as 2-thiouracil, 8-azaguanine, 5-fluorouracil, etc. have been found. However, some of these materials wake some mutants and inhibit protein metabolism of hosts and give damages of medicine. These materials are generally expensive and have a little control effect in actual fields, so that these materials are not used in practice.
As an agent for blocking the contact contagion, sodium alginate is used. However, the application is limited to the TMV-OM and the control effect is insufficient. The agent is ineffective to entomophilous contagion virus such as CMV which is carried by plant lice such as aphid.